1. Technical Field
The present invention relates to systems and methods capable of acquiring necessary data for the monitoring and diagnosis of the cardiovascular system using a heart lung sound.
2. Description of the Related Art
In diagnosing anesthetized patients or seriously affected patients, there is a need to monitor a number of data. By using general monitoring devices currently available, the patient's electrocardiogram, blood pressure, end-tidal carbon dioxide partial pressure, peripheral oxygen saturation and body temperature can be generally monitored.
Although it is not generally monitored, a body fluid content (total blood volume) (below, called “preload” having the same or similar meaning) and a cardiac contractile force can be included as clinically important data.
First, the preload will be described.
For trauma patients or patients undergoing surgery, a rapid change in the blood volume within a short period of time can occur due to bleeding out and the like. At this time, the preload must be known in order to identify the presence or absence of such a change. In other words, when the preload is accurately identified in real time, an appropriate measure such as blood transfusion or fluid infusion can then be taken. Therefore, the preload can be said to be data directly related to the patient's health. Currently, basic monitoring data such as blood pressure or oxygen saturation is acquired using conventional monitoring devices, through which the preload can be indirectly estimated. However, for example, since the blood pressure may be normal until a considerable amount of blood loss occurs, the accuracy is insufficient, thus making effective real-time monitoring is difficult.
As another method for evaluating the preload, “response to fluid administration” can be used. This has been designed based on the fact that, if the blood volume of the patient is insufficient upon fluid administration, there is a response which causes an increase in the blood pressure. If the blood pressure increases after the fluid administration, there is a response (response(+)) and thus the preload will be lowered. If there is no response (response(−)), the preload will be sufficient. The response to fluid administration is a method well-known for evaluating whether the blood volume of the patient is appropriate. This is a concept designed to predict the blood volume prior to administration because the fluid administration itself may cause a harmful situation for the patient.
Indices for completely predicting the response to fluid administration have not been known to date. However, a number of monitoring devices that have recently come into the market have been developed in the direction of self-developing the indices representing a response to fluid administration and displaying them on the screen.
Next, the cardiac contractile force will be described.
The blood pressure may be lowered even though the preload is sufficient. This is because the cardiac contractile force is insufficient. As a device for evaluating the cardiac contractile force, only the echocardiography device is currently available. However, since the echocardiography device requires a high skill level for operation and has difficulties in continual monitoring, it is hard to conveniently use this device in actual clinical practice.
Among the data monitoring devices for monitoring. anesthetized patients or seriously affected patients, examples of typical monitoring devices available in the market today are as follows.
Vigilence® device (Edward Lifescience® company) measures various hemodynamic indices with a blood dilution method, and particularly observes whether the cardiac output (CO) increases by more than 10% to 15% due to the fluid administration, thus assessing the condition of the patient. In the case of using the indices of the aforementioned responsiveness of fluid administration, a time delay can occur because of body heat dilution time. Therefore, when a sudden hemodynamic change occurs, the accuracy is low; particularly, since a long conduit of the catheter penetrates into the heart and mounts on a pulmonary artery, health risks may be high.
In the case of Vigileo® device, e.g., another device of Edward Lifescience® company, a stroke volume variation (SVV) is calculated by acquiring the data in the arterial pressure waveform measured in the radial artery and the like. There is a disadvantage in that there is an invasive mounting on ductus arteriosus. There are reports that there is a large degree of error in situations where the administration of a large amount of vasopressor drugs such as sepsis is required.
In the case of NICOM® device (Chita Medical® company), the total blood volume is estimated based on a change of impedance in the thorax measured by attaching the electrical electrodes to the four corners of the thorax. The present device has a fatal defect in that the accuracy is insufficient and the interference signal is applied by the use of an electrocautery during operation.
In addition, devices for heart ultrasound measurements are manufactured by Philips®, GE®, CardioQ®, zonare® and the like, but they have difficulties in continual monitoring, require a high skill level for operation and have a limitation in providing data necessary for anesthetized patients or seriously affected patients.
In short, the conventional devices have disadvantages in that they use invasive methods to increase accuracy and in that some devices not using the invasive methods have low accuracy, require a high skill level for operation and have difficulties in continual monitoring.
Therefore, there is a need to develop devices for providing the preload and the cardiac contractile force when applied to patients undergoing surgery or severe trauma patients. In particular, there is a need to develop devices capable of high accuracy while using a non-invasive method, having an excellent continual monitoring capacity and providing the data irrespective of the skill level of an operator.
A review of the publications related to the present invention will be described as follows.
U.S. Pat. No. 7,174,203 discloses a system for identifying the condition of the heart by continuously conducting measurements of the electrocardiogram data and heart sound parameters and analyzing the hemodynamic condition. This system has advantages in that it uses a non-invasive method, but the preload and the cardiac contractile force are not provided and thus, it fails to acquire the data essentially required for the procedures of the clinical diagnosis and treatment.
Non-patent document, the 2010 paper, “New Temporal Features for Cardiac Disorder Classification by Heart Sound” discloses an algorithm capable of identifying various kinds of cardiac diseases by analyzing the heart sound data. However, this simply identifies direct diseases of the heart, particularly lesions of heart valves, and it fails to provide the data for monitoring anesthetized patients or seriously affected patients other than patients with basal heart diseases.
Japanese Patent No. 5,230,161 discloses a technique of diagnosing cardiac diseases by synchronizing the heart sound data and the electrocardiogram data. Likewise, this fails to provide the data for monitoring anesthetized patients or seriously affected patients other than patients with basal heart diseases.